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Date:   Mon, 21 Feb 2022 08:15:52 +0800
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Subject: Re: [PATCH] btrfs: Initialize ret to 0 in scrub_simple_mirror()
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To:     Souptick Joarder <jrdr.linux@gmail.com>, clm@fb.com,
        josef@toxicpanda.com, dsterba@suse.com, nathan@kernel.org,
        ndesaulniers@google.com
Cc:     linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org,
        llvm@lists.linux.dev, kernel test robot <lkp@intel.com>
References: <20220220144606.5695-1-jrdr.linux@gmail.com>
From:   Qu Wenruo <quwenruo.btrfs@gmx.com>
In-Reply-To: <20220220144606.5695-1-jrdr.linux@gmail.com>
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On 2022/2/20 22:46, Souptick Joarder wrote:
> From: "Souptick Joarder (HPE)" <jrdr.linux@gmail.com>
>
> Kernel test robot reported below warning ->
> fs/btrfs/scrub.c:3439:2: warning: Undefined or garbage value
> returned to caller [clang-analyzer-core.uninitialized.UndefReturn]
>
> Initialize ret to 0.
>
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Souptick Joarder (HPE) <jrdr.linux@gmail.com>

Although the patch is not yet merged, but I have to say, it's a false aler=
t.

Firstly, the while loop will always get at least one run.

Secondly, in that loop, we either set ret to some error value and break,
or after at least one find_first_extent_item() and scrub_extent() call,
we increase cur_logical and reached the limit of the while loop and exit.

So there is no possible routine to leave @ret uninitialized and returned
to caller.

Thanks,
Qu

> ---
>   fs/btrfs/scrub.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index 4baa8e43d585..5ca7e5ffbc96 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -3325,7 +3325,7 @@ static int scrub_simple_mirror(struct scrub_ctx *s=
ctx,
>   	const u32 max_length =3D SZ_64K;
>   	struct btrfs_path path =3D {};
>   	u64 cur_logical =3D logical_start;
> -	int ret;
> +	int ret =3D 0;
>
>   	/* The range must be inside the bg */
>   	ASSERT(logical_start >=3D bg->start &&